Additives to Silane for Thin Film Silicon Photovoltaic Devices

ABSTRACT

The objective of this invention is to use chemical additives to increase the rate of deposition processes for the amorphous silicon film (αSi:H) and/or the microcrystalline silicon film (μCSi:H), and improve the electrical current generating capability of the deposited films for photoconductive films used in the manufacturing of Thin Film based Photovoltaic (TFPV) devices.

BACKGROUND OF THE INVENTION

Photovoltaic devices (PV) or solar cells are devices which convertsunlight into direct current (DC) electrical power.

Thin Film based Photovoltaic (TFPV) devices have been using bothamorphous silicon film (αSi:H) and microcrystalline silicon film(μCSi:H) for low cost thin film photovoltaic devices. Hydrogenatedamorphous silicon (αSi:H) has been studied for applications in solarcells for several decades. More recently, microcrystalline silicon(μCSi:H) has been studied because it is a suitable material for theintrinsic layer in the bottom cell of thin-film tandem solar cells.

The deposition of αSi:H and μCSi:H on large substrate based photovoltaic(PV) panels has been accomplished primarily using silane (SiH₄) andhydrogen gases (H₂) mixtures. The work have been done in the fieldincludes: US2009/0077805 A1, US2007/0298590 A1), U.S. Pat. No. 6,855,621B2 and JP2005244037. A. Hammad et al (Thin Solid Films 451-452 (2004)255-258) studied the hydrogenated microcrystalline silicon thin filmsusing silane (SiH₄), hydrogen gases (H₂) and disilane (Si₂H₆).

However, the deposition processes are relatively slow (5 Å/sec for αSi:Hand 1-7 Å/sec for μCSi:H) creating a bottle neck in the manufacturing ofTFPV panels. This leads to a lower process tool through-put, which inturn leads to higher cost per Watt for the manufactured panels.

Additionally, deposition of αSi:H and μCSi:H on large substrate basedphotovoltaic (PV) panels with the existing chemistry of SiH₄ and H₂yield solar cells with efficiencies ranging from 6% to 10%, depending,on cell design. The cell efficiency is dependent upon the quality of theαSi:H and μCSi:H deposited, and more specifically related to the grainsize of crystallites in μCSi:H, number of defects and donor impuritiespresent in the film.

Therefore, there is a need of a method for depositing an amorphoussilicon film (αSi:H) and a microcrystalline silicon film (μCSi:H) withincreased deposition rate and increased cell efficiency.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to the use of chemicaladditives to increase the rate of deposition processes, and improve theelectrical current generating capability of the deposited films forphotoconductive films used in the manufacturing of Thin Film basedPhotovoltaic (TFPV) devices.

In one embodiment, the invention provides a method of deposition for asolar grade amorphous silicon film (αSi:H) as a photoconductive film ona substrate, using

-   -   Silane;    -   hydrogen; and    -   at least one additive selected from the group consisting of:        -   (a) higher order straight chain silanes, comprising;            disilane Si₂H₆, trisilane Si₃H₈, tetrasilane Si₄H₁₀,            pentasilane Si₅H₁₂, hexasilane Si₆H₁₄, heptasilane Si₇H₁₆,            octasilane Si₈H₁₈, nonasilane Si₉H₂₀, decasilane Si₁₀H₂₂ and            mixtures thereof;        -   (b) higher order branched silanes, comprising;            2-silyl-trisilane SiH₃—Si(H)(SiH₃)—SiH₃,            2,2-disilyl-trisilane SiH₃—Si(SiH₃)₂—SiH₃,            2-silyl-tetrasilane SiH₃—Si(H)(SiH₃)—SiH₂—SiH₃,            2,3-disilyltetrasilane SiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₃,            2,2-disilyltetrasilane SiH₃—Si(SiH₃)₂—SiH₂—SiH₃,            3-silylpentasilane SiH₃—SiH₂—SiH(SiH₃)—SiH₂—SiH₃,            2-silylpentasilane SiH₃—SiH(SiH₃)—SiH₂SiH₂SiH₃,            2,3-disilylpentasilane SiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃,            2,4-disilylpentasilane SiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₃,            2-silylhexasilane SiH₃—SiH(SiH₃)—(SiH₂)₃SiH₃,            3-silylhexasilane SiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₂SiH₃,            2,2-disilylpentasilane SiH₃—Si(SiH₃)₂—(SiH₂)₂—SiH₃,            3,3-disilylpentasilane SiH₃—SiH₂—Si(SiH₃)₂—SiH₂—SiH₃,            2,2,3-trisilyltetrasilane SiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₃,            2-silylheptasilane SiH₃—SiH(SiH₃)—(SiH₂)₄—SiH₃,            3-silylheptasilane SiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₃—SiH₃,            4-silylheptasilane SiH₃—(SiH₂)₂—SiH(SiH₃)—(SiH₂)₂—SiH₃,            2,2-disilylhexasilane SiH₃—Si(SiH₃)₂—(SiH₂)₃—SiH₃,            2,3-disilylhexasilane SiH₃—SiH(SiH₃)—SiH(SiH₃)—(SiH₂)₂—SiH₃,            2,4-disilylhexasilane            SiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₂—SiH₃,            2,5-disilythexasilane SiH₃—SiH(SiH₃)—(SiH₂)₂—SiH(SiH₃)—SiH₃,            3,3-disilylhexasilane SiH₃—SiH₂—Si(SiH₃)₂—(SiH₂)₂—SiH₃,            3,4-disilylhexasilane            SiH₃—SiH₂—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,2,3            trisilylpentasilane SiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₂—SiH₃,            2,2,4-trisilylpentasilane            SiH₃—Si(SiH₃)₂—SiH₂—SiH(SiH₃)—SiH₃,            2,3,3-trisilylpentasilane            SiH₃—SiH(SiH₃)—Si(SiH₃)₂—SiH₂—SiH₃,            2,3,4-trisilylpentasilane            SiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH(SiH₃)—SiH₃,            2,2,3,3-tetrasilyltetrasilane SiH₃—Si(SiH₃)₂—Si(SiH₃)₂—SiH₃            and mixtures thereof;        -   (c) cyclic silanes, selected from the group consisting of;            cyclotrsilane Si₃H₆, cyclotetrasilane Si₄H₈,            cyclopentasilane Si₅H₁₀, cyclohexasilane Si₆H₁₀, and            mixtures thereof;        -   (d) silyl substituted cyclic silanes, selected from the            group consisting of; silyl cyclotetrasilane SiH3-Si₄H₇,            1,2-disilyl cyclopentasilane (SiH₃)₂—Si₅H₈, silyl            cyclohexasilane SiH₃—Si₆H₁₁, 1,3-disilyl cyclohexasilane            (SiH₃)₂—Si₆H₁₀, and mixtures thereof;        -   (e) silyl substituted silenes, selected from the group            consisting of; 2-tetrasilene SiH₃—SiH═SiH—SiH₃,            2,3-disilyltetrasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₃,            2,3-disilylpentasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₂—SiH₃,            2,5-disilylhexasil-2-ene            SiH₃—Si(SiH₃)═SiH—SiH2-SiH(SiH₃)—SiH₃,            2,3,4-trisilylhexasil-2-ene            SiH₃—Si(SiH₃)═Si(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, and mixtures            thereof;        -   (f) halogen substituted silenes, including;            1,1-dichlordisilane SiHCl₂SiH₃, 1,1,1,2-tetrafluorodislane            SiF₃—SiH₂F, 1,2-dichloro-1,2-difluorotetrasilane            SiHClF—SiClF—SiH₂—SiH₃, 1,1,1-trichlorotrisilane            SiCl₃—SiH₂—SiH₃, 1,1-difluora-1,2,2-trichlorosilane            SiF₂Cl—SiCl₂—SiH₃, chloropentasilane SiH₂Cl—(SiH₂)₃—SiH₃,            and other compounds of the general formula            Si_(w)H_(2w+2-z)X_(z) where X═F, Cl, Br, I; w can be 1 to 20            and z can be 1 to 2w+2; 2-chlorotetrasil-2-ene            SiH₃—SiCl═SiH—SiH₃, 1,1-dichloro-2-fluoropentasil-2-ene            SiHCl₂—SiF═SiH₂—SiH₂—SiH₃, 2,3-dichlorotetrasil-2-ene            SiH₃—SiCl═SiCl—SiH₃, and other compounds of the general            formula Si_(w)H_(2w-z)X′_(z) where X′═F, Cl, Br, I; and, w            can be 2 to 20 and z can be 1 to 2w; and mixtures thereof;            and        -   (g) halogen substituted cyclic silanes, selected from the            group consisting of; chlorocyclopentasilane Si₅H₉Cl,            dodecachlorocyclohexasilane Si₆Cl₁₂,            1-chloro-1fluorocyclopentasilane Si₅H₈FCl, and mixtures            thereof; and the deposited solar grade amorphous silicon            film (αSi:H) thereof.

In another embodiment, the invention provides a method of deposition foramorphous silicon film (αSi:H) or microcrystalline silicon film (μCSi:H)as a photoconductive film on a substrate, using

-   -   Silane;    -   hydrogen;    -   at least one additive selected from the group consisting of        -   (a) higher order straight chain silanes, comprising;            disilane Si₂H₆, trisilane Si₃H₈, tetrasilane Si₄H₁₀,            pentasilane Si₅H₁₂, hexasilane Si₆H₁₄, heptasilane Si₇H₁₆,            octasilane Si₈H₁₈, nonasilane Si₉H₂₀, decasilane Si₁₀H₂₂ and            mixtures thereof;        -   (b) higher order branched silanes, comprising;            2-silyl-trisilane SiH₃—Si(H)(SiH₃)—SiH₃,            2,2-disilyl-trisilane SiH₃—Si(SiH₃)₂—SiH₃,            2-silyl-tetrasilane SiH₃—Si(H)(SiH₃)—SiH₂—SiH₃,            2,3-disilyltetrasilane SiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₃,            2,2-disilyltetrasilane SiH₃—Si(SiH₃)₂—SiH₂—SiH₃,            3-silylpentasilane SiH₃—SiH₂—SiH(SiH₃)—SiH₂—SiH₃,            2-silylpentasilane SiH₃—SiH(SiH₃)—SiH₂—SiH₂—SiH₃,            2,3-disilylpentasilane SiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃,            2,4-disilylpentasilane SiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₃,            2-silylhexasilane SiH₃—SiH(SiH₃)—(SiH₂)₃SiH₃,            3-silylhexasilane SiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₂SiH₃,            2,2-disilylpentasilane SiH₃—Si(SiH₃)₂—(SiH₂)₂—SiH₃,            3,3-disilylpentasilane SiH₃—SiH₂—Si(SiH₃)₂—SiH₂—SiH₃,            2,2,3-trisilyltetrasilane SiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₃,            2-silylheptasilane SiH₃—SiH(SiH₃)—(SiH₂)₄—SiH₃,            3-silylheptasilane SiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₃—SiH₃,            4-silylheptasilane SiH₃—(SiH₂)₂—SiH(SiH₃)—(SiH₂)₂—SiH₃,            2,2-disilylhexasilane SiH₃—Si(SiH₃)₂—(SiH₂)₃—SiH₃,            2,3-disilylhexasilane SiH₃—SiH(SiH₃)—SiH(SiH₃)—(SiH₂)₂—SiH₃,            2,4-disilylhexasilane            SiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₂—SiH₃,            2,5-disilylhexasilane SiH₃—SiH(SiH₃)—(SiH₂)₂—SiH(SiH₃)—SiH₃,            3,3-disilylhexasilane SiH₃—SiH₂—Si(SiH₃)₂—(SiH₂)₂—SiH₃,            3,4-disilylhexasilane            SiH₃—SiH₂—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃,            2,2,3-trisilylpentasilane            SiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₂—SiH₃,            2,2,4-trisilylpentasilane            SiH₃—Si(SiH₃)₂—SiH₂—SiH(SiH₃)—SiH₃,            2,3,3-trisilylpentasilane            SiH₃—SiH(SiH₃)—Si(SiH₃)₂—SiH₂—SiH₃,            2,3,4-trisilylpentasilane            SiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH(SiH₃)—SiH₃,            2,2,3,3-tetrasilyltetrasilane SiH₃—Si(SiH₃)₂—Si(SiH₃)₂—SiH₃            and mixtures thereof;        -   (c) cyclic silanes, selected from the group consisting of            cyclotrisilane Si₃H₆, cyclotetrasilane Si₄H₈,            cyclopentasilane Si₅H₁₀ cyclohexasilane Si₆H₁₀, and mixtures            thereof;        -   (d) silyl substituted cyclic silanes, selected from the            group consisting of; silyl cyclotetrasilane SiH 3-Si₄H₇,            1,2-disilyl cyclopentasilane (SiH₃)₂—Si₅H₈, silyl            cyclohexasilane SiH₃—Si₆H₁₁, 1,3-disilyl cyclohexasilane            (SiH₃)₂—Si₆H₁₀, and mixtures thereof;        -   (e) silyl substituted silenes, selected from the group            consisting of; 2-tetrasilene SiH₃—SiH═SiH—SiH₃,            2,3-disilyltetrasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₃,            2,3-disilylpentasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₂—SiH₃,            2,5-disilylhexasil-2-ene            SiH₃—Si(SiH₃)═SiH—SiH2-SiH(SiH₃)—SiH₃,            2,3,4-trisilylhexasil-2-ene            SiH₃—Si(SiH₃)═Si(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, and mixtures            thereof;    -   and    -   at least one another additive selected from the group        consisting, of:        -   (f) halogen substituted silenes, selected from the group            consisting of; monochlorosilane SiH₃Cl, dichlorosilane            SiH₂Cl₂, trichlorosilane SiHCl₃, tetrachlorosilane (SiCl₄),            chlorodisilane SiH₃—SiH₂Cl, and mixtures thereof;        -   and        -   (g) halogen containing gases, selected from the group,            consisting of; chlorine Cl₂, hydrogen chloride HCl, chlorine            trifluoride ClF₃, nitrogen trifluoride NF₃, fluorine F₂,            hydrogen fluoride HF, bromine Br₂, hydrogen bromide HBr,            hydrogen iodide HI and mixtures thereof;            and the deposited amorphous silicon film (αSi:H) or            microcrystalline silicon film (μCSi:H) thereof.

In yet another embodiment, the invention provides a method of depositionfor a solar grade amorphous silicon film (αSi:H) or a microcrystallinesilicon film (μCSi:H) having high microcrystalline fraction as aphotoconductive film on a substrate, using

-   -   Silane;    -   hydrogen; and    -   at least one additive selected from the group consisting of:        -   (a) halogen substituted higher order silenes, including;            1,1-dichlordisilane SiHCl₂SiH₃, 1,1,1,2-tetrafluorodislane            SiF₃—SiH₂F, 1,2-dichloro-1,2-difluorotetrasilane            SiHClF—SiClF—SiH₂—SiH₃, 1,1,1-trichlorotrisilane            SiCl₃—SiH₂—SiH₃, 1,1-difluoro-1,2,2-trichlorosilane            SiF₂Cl—SiCl₂—SiH₃, chloropentasilane SiH₂Cl—(SiH₂)₃—SiH₃,            and other compounds of the general formula            Si_(w)H_(2w+2-z)X_(z) where X═F, Cl, Br, I; w can be 1 to 20            and z can be 1 to 2w+2; 2-chlorotetrasil-2-ene            SiH₃—SiCl═SiH—SiH₃, 1,1-dichloro-2-fluoropentasil-2-ene            SiHCl₂—SiF═SiH₂—SiH₂—SiH₃, 2,3-dichlorotetrasil-2-ene            SiH₃—SiCl═SiCl—SiH₃, and other compounds of the general            formula SiH_(w)H_(2w-z)X′_(z) where X′═F, Cl, Br, I; and, w            can be 2 to 20 and z can be 1 to 2w; and mixtures thereof;            and        -   (b) halogen substituted cyclic higher order silanes,            selected from the group consisting of;            chlorocyclopentasilane Si₅H₉Cl, dodecachlorocyclohexasilane            Si₆Cl₁₂, 1-chloro-1-fluorocyclopentasilane Si₅H₈Cl, and            mixtures thereof.            and the deposited solar grade amorphous silicon film (αSi:H)            or microcrystalline silicon film (μCSi:H) having high            microcrystalline fraction thereof.

The deposited films in the embodiments disclosed above, provide highdeposition rates, enhanced photoconductivity, solar grade for amorphoussilicon film (αSi:H), and high microcrystalline fraction formicrocrystalline silicon film (μCSi:H).

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1. The Empirical Microstructure Factor R* of hydrogenated siliconαSi:H versus SiH₄ flow rate under different power densities. Thehydrogenated silicon αSi:H was deposited using silane and hydrogen.

FIG. 2. The deposition rate of hydrogenated silicon αSi:H versus SiH₄flow rate under different power densities. The hydrogenated siliconαSi:H was deposited using silane and hydrogen.

FIG. 3. The deposition rate of hydrogenated silicon αSi:H versus theflow rate of the mixture of SiH4 and disilane under different powerdensities. The hydrogenated silicon αSi:H was deposited using silanedisilane and hydrogen.

FIG. 4. The Empirical Microstructure Factor R* of hydrogenated siliconαSi:H versus the flow rate of the mixture of SiH4 and disilane underdifferent power densities. The hydrogenated silicon αSi:H was, depositedusing silane, disilane and hydrogen.

FIG. 5. The microcrystalline fraction versus the mole fractionSiH₃Cl/(SiH₃Cl+Si_(x)H_(y)) %.

FIG. 6. The Activation Energy for deposited microcrystalline film versusthe mole fractions of halogenated silanes SiH₃Cl/SiH₃Cl+Si_(x)H_(y))(%).

DETAILED DESCRIPTION OF THE INVENT ON

In prior arts, Plasma power, frequency, temperature, gas mixing ratiosand pressure have been used to control film structure, thickness andelectrical properties.

The present invention further discloses the use of chemical additives toincrease the rate of deposition processes, and improve the electricalcurrent generating capability of the deposited films for photoconductivefilms used in the manufacturing of Thin Film based Photovoltaic (TFPV)devices.

Increasing the module efficiency is one approach for reducingmanufacturing costs. The present invention discloses the reduction ofmanufacturing costs through the addition of additives to the mixture ofSiH₄ and H₂.

In present invention, the additives are used to increase the depositionrate, and in addition, to control film structure to achieve the bettergrade for the practical use, to optimize crystalline grain sizes, reducethe number of defects and/or minimize or neutralize the effects ofimpurities present as a result of contamination, from the processingenvironment; thus to reduce manufacturing costs.

More specifically, the present invention uses the mixture of silane andhydrogen as the primary source of silicon, and uses additives as theprocess enhancing feature. The process enhancements are significantlygreater than the potential additional cost afforded by the use of highervalue additives. These enhancements lead to a lower cost per unit ofenergy through: (i) a faster deposition rate and better controlling offilm grade resulting, from the addition of relatively low mole fractionsof higher order silanes; and, (ii) more photoconductive film through theaddition of a halogen containing gas or a halogen substituted silanecontaining gas.

The deposition processes include but not limited to Chemical VaporDeposition (CVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), LowPressure Chemical Vapor Deposition (LPCVD), Hot Wire Chemical VaporDeposition (HWCVD), Initiated Chemical Vapor Deposition (ICVD) and SubAtmospheric Chemical Vapor Deposition (SA-CVD).

Process enhancing additives include, but not limited to

(a) Higher order straight chain silanes, including; disilane Si₂H₆,trisilane Si₃H₈, tetrasilane Si₄H₁₀, pentasilane Si₅H₁₂, hexasilaneSi₆H₁₄, heptasilane Si₇H₁₆, octasilane Si₈H₁₈, nonasilane Si₉H₂₀,decasilane Si₁₀H₂₂ and other straight chain silanes following thegeneral formula Si_(x)H_(2x+2) where can be 2-20;

(b) Higher order branched silanes including; 2-silyl-trisilaneSiH₃—Si(H)(SiH₃)—SiH₃, 2,2-disilyl-trisilane SiH₃—Si(SiH₃)₂—SiH₃,2-silyl-tetrasilane SiH₃—Si(H)(SiH₃)—SiH₂—SiH₃, 2,3-disilyltetrasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₃,2,2-disilyltetrasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH₃, 3-silylpentasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH₂—SiH₃,2-silylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH₂—SiH₃ 2,3-disilylpentasilaneSiH₃SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,4-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₃, 2-silylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₃SiH₃, 3-silylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₂SiH₃, 2,2-disilylpentasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,3-disilylpentasilaneSiH₃—SiH₂—Si(SiH₃)₂—SiH₂—SiH₃, 2,2,3-trisilyltetrasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₃, 2-silylheptasilaneSiH₃—SiH(SiH₃)—(SiH₂)₄—SiH₃, 3-silylheptasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₃—SiH₃, 4-silylheptasilaneSiH₃—(SiH₂)₂—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,2-disilylhexasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₃—SiH₃, 2,3-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,4-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2,5-disilylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₂—SiH(SiH₃)—SiH₃, 3,3-disilylhexasilaneSiH₃—SiH₂—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,4-disilylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,2,3-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₂—SiH₃, 2,2,4-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH(SiH₃)—SiH₃, 2,3,3-trisilylpentasilaneSiH₃—SiH(SiH₃)—Si(SiH₃)₂—SiH₂—SiH₃, 2,3,4-trisilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH(SiH₃)—SiH₃, 2,2,3,3-tetrasilyltetrasilaneSiH₃—Si(SiH₃)₂—Si(SiH₃)₂—SiH₃ and any other higher branched silanesunder the general formula Si_(x)H_(2x+2) where x can be 4-20;

(c) Cyclic silanes, including; cyclotrisilane Si₃H₆, cyclotetrasilaneSi₄H₈, cyclopentasilane Si₅H₁₀, cyclohexasilane Si₆H₁₀, and other cyclicsilanes consisting of the general formula Si_(x)H_(2x) where x can be3-20;

(d) Silyl substituted cyclic silanes, including; silyl cyclotetrasilaneSiH3-Si₄H₇, 1,2-disilyl cyclopentasilane (SiH₃)₂—Si₅H₈, cyclohexasilaneSiH₃—Si₆H₁₁, 1,3-disilyl cyclohexasilane (SiH₃)₂—Si₆H₁₀, and other silylsubstituted cyclosilanes of the general formulaSi_(y)H_(3y)—Si_(x)H_(2x-y) where x can be 3 to 20 and y can be 1 to 2x.

e) Silyl substituted silenes, including; 2-tetrasileneSiH₃—SiH═SiH—SiH₃, 2,3-disilyltetrasil-2-eneSiH₃—Si(SiH₃)═Si(SiH₃)—SiH₃, 2,3-disilylpentasil-2-eneSiH₃—Si(SiH₃)═Si(SiH₃)—SiH₂—SiH₃, 2,5-disilylhexasil-2-eneSiH₃—Si(SiH₃)═SiH—SiH₂—SiH(SiH₃)—SiH₃, 2,3,4-trisilylhexasil-2-eneSiH₃—Si(SiH₃)═Si(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, and other silyl substitutedsilenes of the general formula Si_(y)H_(3y)—Si_(x)H_(2x-(y+2)) where xcan be 2-20 and y can be 1 to 2x.

(f) Halogen substituted higher order silenes, including;1,1-dichlordisilane SiHCl₂SiH₃, 1,1,1,2-tetrafluorodislane SiF₃—SiH₂F,1,2-dichloro-1,2-difluorotetrasilane SiHClF—SiClF—SiH₂—SiH₃,1,1,1-trichlorotrisilane SiCl₃—SiH₂—SiH₃,1,1-difluoro-1,2,2-trichlorosilane SiF₂Cl—SiCl₂—SiH₃, chloropentasilaneSiH₂Cl—(SiH₂)₃—SiH₃, and other compounds of the general formulaSi_(w)H_(2w+2-z)X_(z) where X═F, Cl, Br, I; where w can be 1 to 20 and zcan be 1 to 2w+2; 2-chlorotetrasil-2-ene SiH₃—SiCl═SiH—SiH₃,1,1-dichloro-2-fluoropentasil-2-ene SiHCl₂—SiF═SiH₂—SiH₂—SiH₃,2,3-dichlorotetrasil-2-ene SiH₃—SiCl═SiCl—SiH₃, and other compounds ofthe general formula Si_(w)H_(2w-z)X′_(z) where X′═F, Cl, Br, I; and, wcan be 2 to 20 and z can be 1 to 2w.

(g) Halogen substituted cyclic higher order silanes, including;chlorocyclopentasilane Si₅H₉Cl, dodecachlorocyclohexasilane Si₆Cl₁₂,1-chloro-1fluorocyclopentasilane Si₅H₈FCl, and other cyclic silanes ofthe general formula Si_(w)H_(2w-zz)X′_(z) where X′═F, Cl, Br, I; where wcan be 3 to 20 and z can be 1 to 2w.

(h) Halogen substituted silanes, including; monochlorosilane SiH₃Cl,dichlorosilane SiH₂Cl₂, trichlorosilane SiHCl₃, tetrachlorosilane(SiCl₄), and chlorodisilane SiH₃—SiH₂Cl.

(i) Halogen containing gases, including; chlorine Cl₂, hydrogen chlorideHCl, chlorine trifluoride ClF₃, nitrogen trifluoride NF₃, fluorine F₂,hydrogen fluoride HF, bromine Br₂, hydrogen bromide HBr, hydrogen iodideHI and other compounds of these types.

To increase the deposition rate and improve the photoconductivity of thefilm, one embodiment of the present invention uses at least one additiveselected from the groups (a) to (g) shown above in addition of SiH₄ andH₂; yet another embodiment of the present invention uses thecombinations of additives from groups (a) to (e) and additives fromgroups (h) and (i) to further enhance the photoconductivity of the film.

The depositions use 5 to 10% silane; from 0.01 to 5% an additive fromgroups (a) to (g); 0.01 to 5% an additive from groups (h) and (i), andthe rest is hydrogen, where, the flow of hydrogen, silane, anappropriate additive or additives totals 100%.

Working Examples Deposition of Amorphous Silicon Film (αSi:H)

Hydrogen plays a critical role in the properties and formation ofhydrogenated silicon (Si:H) networks. Examples of this would be in themetastability of the optoelectronic properties in amorphous hydrogenatedsilicon which is also known as the Staebler-Wronski Effect (SWE).Another example would be in the crystallization of Si—Si bonds duringmicrocrystalline Si:H growth.

Infrared (IR) spectroscopy is a commonly applied analytical techniqueused to detect the different bending, wagging, and stretching modes (SM)of hydrides in amorphous hydrogenated and microcrystalline silicon. Inthe bulk layer of amorphous hydrogenated silicon there are threecharacteristic absorptions modes; wagging modes at 640 cm⁻¹, a scissorsdoublet or bending mode at 840-890 cm⁻¹ which is assigned to thedi-hyrides, and the stretching modes in the range of 1895-2130 cm⁻¹. Thestretching modes are of great interest due to the fact that they reflectdetailed information related to the bonding environment of hydrogen inthe film.

It is well understood that by using IR to analyze amorphous hydrogenatedsilicon for the Si—H_(x) stretching modes between 1895-2130 cm⁻¹ one canback out ratios of Si—H₂ which is also called the High Stretching Mode(HSM) at 2070-2100 cm⁻¹ and Si—H which is also call the Low StretchingMode (LSM) at 1980-2010 cm⁻¹. Amorphous hydrogenated silicon intrinsic,layers with inferior opto-electronic properties typically are dominatedby Si—H₂ stretching modes.

The Empirical Microstructure Factor (R*) is a calculation where one canback out ratios of HSM and LSM. The Empirical Microstructure Factor isdefined as R*=I_(HSM)/(I_(LSM)+I_(HSM)) where I_(HSM) and I_(LSM)correspond to the integrated absorption strength of the LSM and HSM. Bydefinition, the R* value is the percent Si—H₂ in the film. The smallerthe R* value is, the less percent of Si—H₂ is in the film. In generalfor amorphous hydrogenated silicon to be classified as solar gradematerial you need R*<0.2, or less than 20%.

Plasma Enhanced Chemical Vapor Deposition (PECVD) was used in thepresent invention to deposit thin films of αSi:H for single junctionsolar cells and αSi:H and μCSi:H for tandem solar cells, using silanewith hydrogen and additives.

Deposition of Amorphous Silicon Film (αSi:H)

The Empirical Microstructure Factor (R*) in amorphous hydrogenatedsilicon intrinsic layers produced by using Silane (SiH₄) and hydrogencan be manipulated by changing the total flow of chemical by volume andpower density in a Plasma Enhanced Chemical Vapor Deposition chamber(PECVD).

Materials used to produce αSi:H and μCSi:H based solar cells includefrom 5 to 10% silane; from 0.9 to 1.8% of an additive or additives.Process conditions include a substrate temperature of 25°-500° C. withpreferred temperatures of 150°-250° C. Process conditions include plasmapowers from 10-10,000 watts, power, densities from 019 W/cm² to 1.6W/cm² and chamber pressures from 0.01 torr to 15 torr.

FIG. 1 was a graph showing the Empirical Microstructure Factor R* ofhydrogenated silicon αSi:H deposited versus SiH₄ flow rate underdifferent power densities. The percentage of SiH₄ used was 9.0% and H₂was 91%.

The flow rate of the SiH₄ ranged from 0 to 125 sccm; and the powerdensities were at 0.197, 0.789, 1.382 and 1.58 W/cm².

As the power density increased at lower flow rate range (see the flowrates <50 sccm), the Empirical Microstructure Factors R* tended to beabove 20% for all power densities. As the flow rate increased>50 sccm,as power density increased, the Empirical Microstructure Factors R*started to decrease for all power densities, except for 0.197 W/cm².However, it's interesting to point out that the Empirical MicrostructureFactors R* did not get below 20% at higher flow rates (100 and 125 sccm)for all power densities, except at 0.789 W/cm², which led to theconclusion that these films would not produce a suitable solar gradematerial.

The added value of producing the Empirical Microstructure Factors R*below 20% at high power densities and high flow rates was the benefit ofincreased growth rates of the intrinsic films.

FIG. 2 was a graph showing the deposition (growth) rate versus SiH₄ flowrate under different power densities. The Empirical MicrostructureFactor R* for the data was at 10%. The percentage of SiH₄ used was 9.0%and H₂ was 91%. The flow rate of the SiH₄ ranged from 0 to 125 sccm; andthe power densities were at 0.197, 0.394, 0.592, 0.789, 0.987, 1.184,1.382 and 1.58 W/cm².

FIG. 2 showed that as flow rates and power densities increased, thedeposition rates also increased.

Disilane was used as the at least one of additives for higher ordersilanes shown above in group (a). The disilane used ranged from 0.9% to1.8%.

The deposition rate versus the flow rate of the mixture of silane withdisilane under different power densities had been shown in FIG. 3. Thepercentage of disilane was 0.9%, silane was 8.1%, and hydrogen was 91%.

The flow rate of the mixture of SiH₄ and disilane ranged from 0 to 125sccm; and the power densities were at 0.197, 0.394, 0.592, 0.789, 0.987,1.184, 1.382 and 1.58 W/cm².

By using at least one of these higher order silanes as an additive tosilane in the deposition process, the amorphous phase deposition(growth) rate significantly increased as the flow rate increased at allpower densities compared to the neat silane films shown in FIG. 2.

FIG. 4 illustrated Empirical Microstructure Factor R* as a function ofthe flow rate of mixture of silane with trisilane at different powerdensities, the trisilane was used as at least one additive. Thepercentage of Trisilane was 0.9%, Silane was at 8.1%, and Hydrogen wasat 91%. The flow rate of the mixture of SiH₄ and trisilane ranged from 0to 125 sccm; and the power densities were at 0.197, 0.394, 0.592, 0.789,0.987, 1.184, 1.382 and 1.58 W/cm².

FIG. 4 has shown that as the flow rates of the mixture of silane andtrisilane increased, R* value, that is, the % of Si—H₂ in the filmdecreased to less than 20% for all power densities greater than andequal to 0.789 W/cm². This gave the add benefit of the increased growthrate with the Empirical Microstructure Factor R* below 20% to produce asuitable solar grade material.

However, the R* values did not reach <20% for the power densities lessthan and equal to 0.5923 W/cm². This indicated that these films wouldnot be a suitable solar grade material.

Thus, to deposit a suitable solar grade silicon film, both the EmpiricalMicrostructure Factor R* value and the deposition rate are importantfactors.

As shown above in FIG. 4, although the deposition rates were higher atpower densities less than and equal to 0.5923 W/cm² (comparing with thedata shown in FIG. 2—no disilane used), however, due to the higher R*values (>20%), no suitable solar grade films can be deposited withtrisilane as an additive at those power densities.

Deposition of Microcrystalline Silicon Film (μCSi:H)

The dual benefit of faster deposition and higher photoconductance can beachieved through the use of dual functional additives designed toincorporate the chemical features required to achieve both types ofprocess enhancement.

The growth rate enhancement and photoconductivity maintaining areachieved through addition of at least one higher order silane fromgroups (a) to (e), while by incorporating at least one additional moietyfrom groups (h) and (i), such as a halogen, on the silane or, higherorder silane, microcrystalline fraction is increased and the impact offilm defects and impurities is reduced.

For example, molecules such as monchlorosilane (SiH₃Cl or MCS),dichlorosilane (SiH₂Cl₂), chlorodisilane (Si₂H₅Cl₂) can be used as theat least one additional additives, in addition to growth rate enhancinghigher order silane, such as disilane and trisilane to the processyielding higher fractions of microcrystalinity in the deposited film.

PECVD process is used in depositing the microcrystalline silicon film(μCSi:H).

For the data obtained in FIG. 5, monchlorosilane (SiH₃Cl) is used as theat least one additional additive, the higher order silanes arerepresented by Si_(x)H_(y), wherein x=2 to 20 and y=6 to 42.

The mixture of the halogenated silane SiH₃Cl with silane (SiH₄) and,higher order silanes (Si_(x)H_(y)) is represented by(SiH₃Cl+Si_(x)H_(y)), wherein x=2 to 20 and y=6 to 42. The mole fractionSiH₃Cl/(SiH₃Cl+Si_(x)H_(y)) % is the ratio of the halogenated silaneSiH₃Cl (MCS) to the mixture of the halogenated silane SiH₃Cl with silane(SiH₄) and higher order silanes (Si_(x)H_(y)).

The flow rate of H₂ ranges from 91 to 99%, the flow rate of the mixtureranges from 1% to 9%. The preferred embodiment of the example is(SiH₃Cl+Si_(x)H_(y)) flows of 1-2% and H₂ flows of 98-99% based on thereactor plasma frequency of 13.56 MHz.

Those skilled in the art will realize that higher plasma frequencies,such as 40.68 MHz, will permit higher, relative (SiH₃Cl+Si_(x)H_(y))flows.

The film deposition in FIG. 5 is performed at 13.56 MHz using 1-9%silane, 1-9% higher order silane, and 1-9% SiH₃Cl, with total Sicontaining moieties not exceeding 9% ((SiH₄+SiH₃Cl+Si_(x)H_(y))<or equal9%). The preferred embodiment of the present example is to use 1-2%silane, 0.1-0.2% higher order silane (Si_(x)H_(y)), 0.1-0.2% MCS, andwith balance being hydrogen.

FIG. 5 shows the results of the change of the microcrystalline fractionas the function of the mole fraction of SiH₃Cl/(SiH₃Cl+Si_(x)H_(y)) %.Applicants have found that all the higher order silanes functioned thesame.

When no SiH₃Cl is added, the Microcrystalline fraction is around 38%.The microcrystalline fraction reaches an optimum value about 51% atapproximately 0.18 mole fraction of SiH₃Cl/(SiH₃Cl+Si_(x)H_(y)) %, andtrends down until the film becomes amorphous at >0.5 mole fraction. Anoptimal amount of Cl added to the deposition aids in the nucleationprocess for microcrystalline formation. As more Cl is added the filmtrends towards the amorphous phase. The specific mechanisms yieldingoptimized microcrystalline fractions at a given Cl partial pressure inthe plasma are not fully understood but are suspected of being relatedto Cl aiding in the microcrystalline seeding process. Excess Cl disruptsthe structured deposition of microcrystalline yielding higher degrees ofamorphous silicon fractions within the deposited film.

FIG. 5 clearly indicates that the use of halogen substituted silanes inaddition of higher order silanes will increase the microcrystallinefraction, providing an optimal band gap for the microcrystalline layerof 1.2 eV as part of the tandem solar cell.

The film deposition conditions used in FIG. 6 are the same as in FIG. 5.

FIG. 6 shows the dark current activation energy versus the molefractions of halogenated silanes SiH₃Cl/(SiH₃Cl+Si_(x)H_(y)) %, whereinSi_(x)H_(y)═SiH₄+Si_(x)H_(y) wherein x=2-20 and y=6-42. The dark currentactivation energy is the energy required to generate charge carriers inthe absence of light for deposited microcrystalline

As demonstrated in FIG. 6, the dark current activation energy (E_(ACT))is impacted by the addition of chlorine to the process. The effect ofchlorine addition increases dark current E_(ACT) from 0.2 eV toapproximately 0.6 eV indicating that the effects of chlorine additionare reduction of the effects of donor impurities such as oxygen on thedeposited microcrystalline film at low mole fractions from 0.10 to 0.40of halogenated silanes SiH₃Cl/(SiH₃Cl+Si_(x)H_(y)) %, compared to theabsence of added chlorine.

As shown in FIG. 6, at high chlorine mole fractions>0.5, E_(ACT)increases as the film transitions from microcrystalline to amorphousphase.

Those results are believed to be attributed to Cl acting as an impurityscavenger reducing the doping capacity, of impurities. The enhancementin photoconductivity is realized by shifting the Fermi level to mid bandgap for the enhanced growth rate intrinsic microcrystalline film.

The shift in Fermi level to the middle of the band gap at ca. 0.6 eVprovides the optimal electrical bias for, a p-i-n type photovoltaicdevice that is the subject of this invention. The electrical biasinherent to the p-i-n structure aids in separation of charge carrierscreated in the intrinsic Si layer thus leading to higher degree ofcurrent extraction and higher degree of solar cell efficiency. The useof the appropriate quantity of halogen during deposition, from 0.1 to0.4 mole fraction of the silane containing moieties, yields a film thatis less impacted from the defects, such as impurity incorporation, thatcan occur during higher deposition rates.

Figures 5 and 6 have demonstrated that the use of higher order silanesand Halogen substituted silanes will increase the deposition rate, themicrocrystalline fraction, and enhance the photoconductivity of thefilm. The present invention has demonstrated that the de position ofαSi:H and μCSi:H at deposition rates 2-20 times higher than industryaverages reported above. These include deposition rates for αSi:H of10-200 Å/sec and for μCSi:H of 2-100 Å/sec.

The deposited αSi:H films for formation of single junction solar cellshad efficiencies of 5-15%. The deposited αSi:H and μCSi:H films forforming tandem junction solar cells had efficiencies of 7-20%. Solarcell efficiency is defined as: Solar cell efficiency (%)=(Power out(W)×100%)/(Area (m²)×1000 W/m²). These efficiency improvements were theresult from the addition of additives to the deposited films yieldingenhanced photoconductivity.

The foregoing examples and description of the embodiments should betaken as illustrating, rather than as limiting the present invention asdefined by the claims. As will be readily appreciated, numerousvariations and combinations of the features set forth above can beutilized without departing from the present invention as set forth inthe claims. Such variations are intended to be included within the scopeof the following claims.

1. A method of deposition for a solar grade amorphous silicon film(αSi:H) as a photoconductive film on a substrate, using Silane;hydrogen; and at least one additive selected from the group consistingof: (a) higher order straight chain silanes, comprising; disilane Si₂H₆,trisilane Si₃H₈, tetrasilane Si₄H₁₀, pentasilane Si₅H₁₂, hexasilaneSi₆H₁₄, heptasilane Si₇H₁₆, octasilane Si₈H₁₈, nonasilane Si₉H₂₀,decasilane Si₁₀H₂₂ and mixtures thereof; (b) higher order branchedsilanes, comprising; 2-silyl-trisilane SiH₃—Si(H)(SiH₃)—SiH₃,2,2-disilyl-trisilane SiH₃—Si(SiH₃)₂—SiH₃, 2-silyl-tetrasilaneSiH₃—Si(H)(SiH₃)—SiH₂—SiH₃, 2,3-disilyltetrasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₃, 2,2-disilyltetrasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH₃, 3-silylpentasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2-silylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH₂—SiH₃, 2,3-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,4-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₃, 2-silylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₃SiH₃, 3-silylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₂SiH₃, 2,2-disilylpentasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,3-disilylpentasilaneSiH₃—SiH₂—Si(SiH₃)₂—SiH₂—SiH₃, 2,2,3-trisilyltetrasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₃, 2-silylheptasilaneSiH₃—SiH(SiH₃)—(SiH₂)₄—SiH₃, 3-silylheptasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₃—SiH₃, 4-silylheptasilaneSiH₃—(SiH₂)₂—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,2-disilylhexasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₃—SiH₃, 2,3-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,4-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2,5-disilylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₂—SiH(SiH₃)—SiH₃, 3,3-disilylhexasilaneSiH₃—SiH₂—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,4-disilylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,2,3-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₂—SiH₃, 2,2,4-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH(SiH₃)—SiH₃, 2,3,3-trisilylpentasilaneSiH₃—SiH(SiH₃)—Si(SiH₃)₂—SiH₂—SiH₃, 2,3,4-trisilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH(SiH₃)—SiH₃, 2,2,3,3-tetrasilyltetrasilaneSiH₃—Si(SiH₃)₂—Si(SiH₃)₂—SiH₃ and mixtures thereof; (c) cyclic silanes,selected from the group consisting of; cyclotrisilane Si₃H₆,cyclotetrasilane Si₄H₈, cyclopentasilane Si₅H₁₀, cyclohexasilane Si₆H₁₀,and mixtures thereof; (d) silyl substituted cyclic silanes, selectedfrom the group consisting of; silyl cyclotetrasilane SiH3-Si₄H₇,1,2-disilyl cyclopentasilane (SiH₃)₂—Si₅H₈, silyl cyclohexasilaneSiH₃—Si₆H₁₁, 1,3-disilyl cyclohexasilane (SiH₃)₂—Si₆H₁₀, and mixturesthereof; (e) silyl substituted silanes, selected from the groupconsisting of; 2-tetrasilane SiH₃—SiH═SiH—SiH₃,2,3-disilyltetrasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₃,2,3-disilylpentasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₂—SiH₃,2,5-disilylhexasil-2-ene SiH₃—Si(SiH₃)═SiH—SiH2-SiH(SiH₃)—SiH₃,2,3,4-trisilylhexasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃,and mixtures thereof; (f) halogen substituted silanes, including;1,1-dichlordisilane SiHCl₂SiH₃, 1,1,1,2-tetrafluorodislane SiF₃—SiH₂F,1,2-dichloro-1,2-difluorotetrasilane SiHClF—SiClF—SiH₂—SiH₃,1,1,1-trichlorotrisilane SiCl₃—SiH₂—SiH₃,1,1-difluoro-1,2,2-trichlorosilane SiF₂Cl—SiCl₂—SiH₃, chloropentasilaneSiH₂Cl—(SiH₂)₃—SiH₃, and other compounds of the general formulaSi_(w)H_(2w+2-z)X_(z) where X═F, Cl, Br, I; w can be 1 to 20 and z canbe 1 to 2w+2; 2-chlorotetrasil-2-ene SiH₃—SiCl═SiH—SiH₃,1,1-dichloro-2-fluoropentasil-2-ene SiHCl₂—SiF═SiH₂—SiH₂—SiH₃,2,3-dichlorotetrasil-2-ene SiH₃—SiCl═SiCl—SiH₃, and other compounds ofthe general formula Si_(w)H_(2w-z)X′_(z) where X′═F, Cl, Br, I; and, wcan be 2 to 20 and z can be 1 to 2w; and mixtures thereof; and (g)halogen substituted cyclic silanes, selected from the group consistingof; chlorocyclopentasilane Si₅H₉Cl, dodecachlorocyclohexasilane Si₆Cl₁₂,1-chloro-1fluorocyclopentasilane Si₅H₈FCl, and mixtures thereof.
 2. Themethod of deposition for the solar grade amorphous silicon film (αSi:H)of claim 1, wherein the silane used is at 5 to 10%, and the at least oneadditive used is at 0.01 to 5%, and the rest is hydrogen.
 3. The methodof deposition for the solar grade amorphous silicon film (αSi:H) ofclaim 1, wherein the deposition is performed at a substrate temperatureof 25°-500° C., and pressure of 0.01 torr to 15 torr.
 4. The method ofdeposition for the solar grade amorphous silicon film (αSi:H) of claim3, wherein the substrate temperature is at 150°-250° C.
 5. The method ofdeposition for the solar grade amorphous silicon film (αSi:H) of claim1, wherein the deposition is a process selected from the groupconsisting of Chemical Vapor Deposition (CVD), Plasma Enhanced ChemicalVapor Deposition (PECVD), Low Pressure Chemical Vapor Deposition(LPCVD), Hot Wire Chemical Vapor Deposition (HWCVD), Initiated ChemicalVapor Deposition (ICVD) and Sub Atmospheric Chemical Vapor Deposition(SA-CVD).
 6. The method of deposition for the solar grade amorphoussilicon film (αSi:H) of claim 1, wherein the deposition is a plasmaenhanced chemical vapor deposition at a plasma power density rangingfrom 0.19-1.6 W/cm² and a plasma frequency ranging from 13.56 to 40.68MHz.
 7. The method of deposition for the solar grade amorphous siliconfilm (αSi:H) of claim 6 having a deposition rate ranging from 10-200Å/sec.
 8. The method of deposition for the solar grade amorphous siliconfilm (αSi:H) of claim 6, wherein a deposited film provides a singlejunction solar cell having efficiencies of 5-15%; and a tandem junctionsolar cell having efficiencies of 7-20%.
 9. A solar grade amorphoussilicon film (αSi:H) deposited using silane, hydrogen and at least oneadditive selected from the group consisting of: (a) higher orderstraight chain silanes, comprising; disilane Si₂H₆, trisilane Si₃H₈,tetrasilane Si₄H₁₀, pentasilane Si₅H₁₂, hexasilane Si₆H₁₄, heptasilaneSi₇H₁₆, octasilane Si₈H₁₈, nonasilane Si₉H₂₀, decasilane Si₁₀H₂₂ andmixtures thereof; (b) higher order branched silanes, comprising;2-silyl-trisilane SiH₃—Si(H)(SiH₃)—SiH₃, 2,2-disilyl-trisilaneSiH₃—Si(SiH₃)₂—SiH₃, 2-silyl-tetrasilane SiH₃—Si(H)(SiH₃)—SiH₂—SiH₃,2,3-disilyltetrasilane SiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₃,2,2-disilyltetrasilane SiH₃—Si(SiH₃)₂—SiH₂—SiH₃, 3-silylpentasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2-silylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH₂—SiH₃, 2,3-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,4-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₃, 2-silylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₃SiH₃, 3-silylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₂SiH₃, 2,2-disilylpentasilane SiH₃—Si(SiH₃)₂(SiH₂)₂—SiH₃, 3,3-disilylpentasilane SiH₃—SiH₂—Si(SiH₃)₂—SiH₂—SiH₃,2,2,3-trisilyltetrasilane SiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₃,2-silylheptasilane SiH₃—SiH(SiH₃)—(SiH₂)₄—SiH₃, 3-silylheptasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₃—SiH₃, 4-silylheptasilaneSiH₃—(SiH₂)₂—SiH(SiH₃)—(SiH₂)₂-—SiH₃, 2,2-disilylhexasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₃—SiH₃, 2,3-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,4-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2,5-disilylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₂—SiH(SiH₃)—SiH₃, 3,3-disilylhexasilaneSiH₃—SiH₂—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,4-disilylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,2,3-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₂—SiH₃, 2,2,4-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH(SiH₃)—SiH₃, 2,3,3-trisilylpentasilaneSiH₃—SiH(SiH₃)—Si(SiH₃)₂—SiH₂—SiH₃, 2,3,4-trisilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH(SiH₃)—SiH₃, 2,2,3,3-tetrasilyltetrasilaneSiH₃—Si(SiH₃)₂—Si(SiH₃)₂—SiH₃ and mixtures thereof; (c) cyclic silanes,selected from the group consisting of; cyclotrisilane Si₃H₆,cyclotetrasilane Si₄H₈, cyclopentasilane Si₅H₁₀, cyclohexasilane Si₆H₁₀,and mixtures thereof; (d) silyl substituted cyclic silanes, selectedfrom the group consisting of; silyl cyclotetrasilane SiH₃—Si₄H₇,1,2-disilyl cyclopentasilane (SiH₃)₂—Si₅H₈, silyl cyclohexasilaneSiH₃—Si₆H₁₁, 1,3-disilyl cyclohexasilane (SiH₃)₂—Si₆H₁₀, and mixturesthereof; (e) silyl substituted silanes, selected from the groupconsisting of; 2-tetrasilane SiH₃—SiH═SiH—SiH₃,2,3-disilyltetrasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₃,2,3-disilylpentasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₂—SiH₃,2,5-disilylhexasil-2-ene SiH₃—Si(SiH₃)═SiH—SiH2-SiH(SiH₃)—SiH₃,2,3,4-trisilylhexasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃,and mixtures thereof; (f) halogen substituted higher order silanes,including; 1,1-dichlordisilane SiHCl₂SiH₃, 1,1,1,2-tetrafluorodislaneSiF₃—SiH₂F, 1,2-dichloro-1,2-difluorotetrasilane SiHClF—SiClF—SiH₂—SiH₃,1,1,1-trichlorotrisilane SiCl₃—SiH₂—SiH₃,1,1-difluoro-1,2,2-trichlorosilane SiF₂Cl—SiCl₂—SiH₃, chloropentasilaneSiH₂Cl—(SiH₂)₃—SiH₃, and other compounds of the general formulaSi_(w)H_(2w+2-z)X_(z) where X═F, Cl, Br, I; w can be 1 to 20 and z canbe 1 to 2w+2; 2-chlorotetrasil-2-ene SiH₃—SiCl═SiH—SiH₃,1,1-dichloro-2-fluoropentasil-2-ene SiHCl₂—SiF═SiH₂—SiH₂—SiH₃,2,3-dichlorotetrasil-2-ene SiH₃—SiCl═SiCl—SiH₃, and other compounds ofthe general formula Si_(w)H_(2w-z)X′_(z) where X′═F, Cl, Br, I; and, wcan be 2 to 20 and z can be 1 to 2w; and mixtures thereof; and (g)halogen substituted cyclic higher order silanes, selected from the groupconsisting of; chlorocyclopentasilane Si₅H₉Cl,dodecachlorocyclohexasilane Si₆Cl₁₂, 1-chloro-1fluorocyclopentasilaneSi₅H₈Cl, and mixtures thereof.
 10. The solar grade amorphous siliconfilm (αSi:H) of claim 9 wherein the silane used is at 5 to 10%, the atleast one additive used is at 0.01 to 5%, and the rest is hydrogen. 11.The solar grade amorphous silicon film (αSi:H) of claim 9 is depositedat a substrate temperature of 25°-500° C., and pressure of 0.01 torr to15 torr.
 12. The solar grade amorphous silicon film (αSi:H) of claim 11is deposited with a substrate temperature of 150°-250° C.
 13. The solargrade amorphous silicon film (αSi:H) of claim 9 provides an EmpiricalMicrostructure Factor R* less than 20%, wherein the EmpiricalMicrostructure Factor R* is defined as R*=I_(HSM)/(I_(LSM)+I_(HSM));wherein I_(HSM) and I_(LSM) correspond to the integrated absorptionstrength of Si—H₂, or the High Stretching Mode (HSM) at 2070-2100 cm⁻¹and the integrated absorption strength of Si—H, or the Low StretchingMode (LSM) at 1980-2010 cm⁻¹.
 14. The solar grade amorphous silicon film(αSi:H) of claim 9 is deposited with a process selected from the groupconsisting of Chemical Vapor Deposition (CVD), Plasma Enhanced ChemicalVapor Deposition (PECVD), Low Pressure Chemical Vapor Deposition(LPCVD), Hot Wire Chemical Vapor Deposition (HWCVD), Initiated ChemicalVapor Deposition (ICVD) and Sub Atmospheric Chemical Vapor Deposition(SA-CVD).
 15. The solar grade amorphous silicon film (αSi:H) of claim 9is deposited with a plasma enhanced chemical vapor deposition at aplasma power density ranging from 0.19-1.6 W/cm² and a plasma frequencyranging from 13.56 to 40.68 MHz.
 16. The solar grade amorphous siliconfilm (αSi:H) of claim 15 is deposited with a deposition rate of 10-200Å/sec.
 17. The solar grade amorphous silicon film (αSi:H) of claim 15provides a single junction solar cell having efficiencies of 5-15%; anda tandem junction solar cell having efficiencies of 7-20%.
 18. A methodof deposition for amorphous silicon film (αSi:H) or microcrystallinesilicon film (μCSi:H) as a photoconductive film on a substrate, usingSilane; hydrogen; at least one additive selected from the groupconsisting of: (a) higher order straight chain silanes, comprising;disilane Si₂H₆, trisilane Si₃H₈, tetrasilane Si₄H₁₀, pentasilane Si₅H₁₂,hexasilane Si₆H₁₄, heptasilane Si₇H₁₆, octasilane Si₈H₁₈, nonasilaneSi₉H₂₀ decasilane Si₁₀H₂₂ and mixtures thereof; (b) higher orderbranched silanes, comprising; 2-silyl-trisilane SiH₃—Si(H)(SiH₃)—SiH₃,2,2-disilyl-trisilane SiH₃—Si(SiH₃)₂—SiH₃, 2-silyl-tetrasilaneSiH₃—Si(H)(SiH₃)—SiH₂—SiH₃, 2,3-disilyltetrasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₃, 2,2-disilyltetrasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH₃, 3-silylpentasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2-silylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH₂—SiH₃, 2,3-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,4-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₃, 2-silylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₃SiH₃, 3-silylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₂SiH₃, 2,2-disilylpentasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,3-disilylpentasilaneSiH₃—SiH₂—Si(SiH₃)₂—SiH₂—SiH₃, 2,2,3-trisilyltetrasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₃, 2-silylheptasilaneSiH₃—SiH(SiH₃)—(SiH₂)₄—SiH₃, 3-silylheptasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₃—SiH₃, 4-silylheptasilaneSiH₃—(SiH₂)₂—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,2-disilylhexasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₃—SiH₃, 2,3-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,4-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2,5-disilylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₂—SiH(SiH₃)—SiH₃, 3,3-disilylhexasilaneSiH₃—SiH₂—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,4-disilylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,2,3-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₂—SiH₃, 2,2,4-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH(SiH₃)—SiH₃, 2,3,3-trisilylpentasilaneSiH₃—SiH(SiH₃)—Si(SiH₃)₂—SiH₂—SiH₃, 2,3,4-trisilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH(SiH₃)—SiH₃, 2,2,3,3-tetrasilyltetrasilaneSiH₃—Si(SiH₃)₂—Si(SiH₃)₂—SiH₃ and mixtures thereof; (c) cyclic silanes,selected from the group consisting of; cyclotrisilane Si₃H₆,cyclotetrasilane Si₄H₈, cyclopentasilane Si₅H₁₀, cyclohexasilane Si₆H₁₀,and mixtures thereof; (d) silyl substituted cyclic silanes, selectedfrom the group consisting of; silyl cyclotetrasilane SiH3-Si₄H₇,1,2-disilyl cyclopentasilane (SiH₃)₂—Si₅H₈, silyl cyclohexasilaneSiH₃—Si₆H₁₁, 1,3-disilyl cyclohexasilane (SiH₃)₂—Si₆H₁₀, and mixturesthereof; (e) silyl substituted silanes, selected from the groupconsisting of; 2-tetrasilane SiH₃—SiH═SiH—SiH₃,2,3-disilyltetrasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₃,2,3-disilylpentasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₂—SiH₃,2,5-disilylhexasil-2-ene SiH₃—Si(SiH₃)═SiH—SiH2-SiH(SiH₃)—SiH₃,2,3,4-trisilylhexasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃,and mixtures thereof; and at least one another additive selected fromthe group consisting of: (f) halogen substituted silanes, selected fromthe group consisting of; monochlorosilane SiH₃Cl, dichlorosilaneSiH₂Cl₂, trichlorosilane SiHCl₃, tetrachlorosilane (SiCl₄),chlorodisilane SiH₃—SiH₂Cl, and mixtures thereof; and (g) halogencontaining gases, selected from the group consisting of; chlorine Cl₂,hydrogen chloride HCl, chlorine trifluoride ClF₃, nitrogen trifluorideNF₃, fluorine F₂, hydrogen fluoride HF, bromine Br₂, hydrogen bromideHBr, hydrogen iodide HI and mixtures thereof.
 19. The method ofdeposition for the amorphous silicon film (αSi:H) or themicrocrystalline silicon film (μCSi:H) of claim 18 wherein the silaneused is at 5 to 10%, the at least one additive used is at 0.01 to 5%,and at least one another additive is used at 0.01 to 5%, and the rest ishydrogen.
 20. The method of deposition for the amorphous silicon film(αSi:H) or the microcrystalline silicon film (μCSi:H) of claim 18wherein the deposition is performed at a substrate temperature of25°-500° C., and pressure of 0.01 torr to 15 torr.
 21. The method ofdeposition for the amorphous silicon film (αSi:H) or themicrocrystalline silicon film (μCSi:H) of claim 18 wherein thedeposition is a process selected from the group consisting of ChemicalVapor Deposition (CVD), Plasma Enhanced Chemical Vapor Deposition(PECVD), Low Pressure Chemical Vapor Deposition (LPCVD), Hot WireChemical Vapor Deposition (HWCVD), Initiated Chemical Vapor Deposition(ICVD) and Sub Atmospheric Chemical Vapor Deposition (SA-CVD).
 22. Themethod of deposition for the amorphous silicon film (αSi:H) or themicrocrystalline silicon film (μCSi:H) of claim 18 wherein thedeposition is a plasma enhanced chemical vapor deposition at a plasmapower density ranging from 0.19-1.6 W/cm² and a plasma frequency rangingfrom 13.56 to 40.68 MHz.
 23. The method of deposition for the amorphoussilicon film (αSi:H) or the microcrystalline silicon film (μCSi:H) ofclaim 18 having a deposition rate of 10-200 Å/sec for amorphous siliconfilm (αSi:H) and 10-100 Å/sec for microcrystalline silicon film(μCSi:H).
 24. The method of deposition for the amorphous silicon film(αSi:H) or the microcrystalline silicon film (μCSi:H) of claim 18wherein the deposited amorphous silicon film (αSi:H) provides a singlejunction solar cell having efficiencies of 5-15%; and the depositedamorphous silicon film (αSi:H) or microcrystalline silicon film (μCSi:H)provides a tandem junction solar cell having efficiencies of 7-20%. 25.A solar grade amorphous silicon film (αSi:H) or microcrystalline siliconfilm (μCSi:H) having high microcrystalline fraction deposited usingSilane; hydrogen; at least one additive selected from the groupconsisting of: (a) higher order straight chain silanes, comprising;disilane Si₂H₆, trisilane Si₃H₈, tetrasilane Si₄H₁₀, pentasilane Si₅H₁₂,hexasilane Si₆H₁₄, heptasilane Si₇H₁₆, octasilane Si₈H₁₈, nonasilaneSi₉H₂₀, decasilane Si₁₀H₂₂ and mixtures thereof; (b) higher orderbranched silanes, comprising; 2-silyl-trisilane SiH₃—Si(H)(SiH₃)—SiH₃,2,2-disilyl-trisilane SiH₃—Si(SiH₃)₂—SiH₃, 2-silyl-tetrasilaneSiH₃—Si(H)(SiH₃)—SiH₂—SiH₃, 2,3-disilyltetrasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₃, 2,2-disilyltetrasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH₃, 3-silylpentasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2-silylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH₂—SiH₃, 2,3-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,4-disilylpentasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₃, 2-silylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₃SiH₃, 3-silylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₂SiH₃, 2,2-disilylpentasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,3-disilylpentasilaneSiH₃—SiH₂—Si(SiH₃)₂—SiH₂—SiH₃, 2,2,3-trisilyltetrasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₃, 2-silylheptasilaneSiH₃—SiH(SiH₃)—(SiH₂)₄—SiH₃, 3-silylheptasilaneSiH₃—SiH₂—SiH(SiH₃)—(SiH₂)₃—SiH₃, 4-silylheptasilaneSiH₃—(SiH₂)₂—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,2-disilylhexasilaneSiH₃—Si(SiH₃)₂—(SiH₂)₃—SiH₃, 2,3-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—(SiH₂)₂—SiH₃, 2,4-disilylhexasilaneSiH₃—SiH(SiH₃)—SiH₂—SiH(SiH₃)—SiH₂—SiH₃, 2,5-disilylhexasilaneSiH₃—SiH(SiH₃)—(SiH₂)₂—SiH(SiH₃)—SiH₃, 3,3-disilylhexasilaneSiH₃—SiH₂—Si(SiH₃)₂—(SiH₂)₂—SiH₃, 3,4-disilylhexasilaneSiH₃—SiH₂—SiH(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃, 2,2,3-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH(SiH₃)—SiH₂—SiH₃, 2,2,4-trisilylpentasilaneSiH₃—Si(SiH₃)₂—SiH₂—SiH(SiH₃)—SiH₃, 2,3,3-trisilylpentasilaneSiH₃—SiH(SiH₃)—Si(SiH₃)₂SiH₂—SiH₃, 2,3,4-trisilylpentasilaneSiH₃—SiH(SiH₃)—SiH(SiH₃)—SiH(SiH₃)—SiH₃, 2,2,3,3-tetrasilyltetrasilaneSiH₃—Si(SiH₃)₂—Si(SiH₃)₂SiH₃ and mixtures thereof; (c) cyclic silanes,selected from the group consisting of; cyclotrisilane Si₃H₆,cyclotetrasilane Si₄H₈, cyclopentasilane Si₅H₁₀, cyclohexasilane Si₆H₁₀,and mixtures thereof; (d) silyl substituted cyclic silanes, selectedfrom the group consisting of; silyl cyclotetrasilane SiH3-Si₄H₇,1,2-disilyl cyclopentasilane (SiH₃)₂—Si₅H₈, silyl cyclohexasilaneSiH₃—Si₆H₁₁, 1,3-disilyl cyclohexasilane (SiH₃)₂—Si₆H₁₀, and mixturesthereof; (e) silyl substituted silanes, selected from the groupconsisting of; 2-tetrasilane SiH₃—SiH═SiH—SiH₃,2,3-disilyltetrasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₃,2,3-disilylpentasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH₂—SiH₃,2,5-disilylhexasil-2-ene SiH₃—Si(SiH₃)═SiH—SiH2-SiH(SiH₃)—SiH₃,2,3,4-trisilylhexasil-2-ene SiH₃—Si(SiH₃)═Si(SiH₃)—SiH(SiH₃)—SiH₂—SiH₃,and mixtures thereof; and at least one additive selected from the groupconsisting of: (f) halogen substituted silanes, selected from the groupconsisting of; monochlorosilane SiH₃Cl, dichlorosilane SiH₂Cl₂,trichlorosilane SiHCl₃, tetrachlorosilane (SiCl₄), chlorodisilaneSiH₃—SiH₂Cl, and mixtures thereof; and (g) halogen containing gases,selected from the group consisting of; chlorine Cl₂, hydrogen chlorideHCl, chlorine trifluoride ClF₃, nitrogen trifluoride NF₃, fluorine F₂,hydrogen fluoride HF, bromine Br₂, hydrogen bromide HBr, hydrogen iodideHI and mixtures thereof.
 26. The solar grade amorphous silicon film(αSi:H) or the microcrystalline silicon film (μCSi:H) having highmicrocrystalline fraction of claim 25 is deposited with the silane at 5to 10%, the at least one additive used is at 0.01 to 5%, the at leastone another additive is used at 0.01 to 5%, and the rest is hydrogen.27. The solar grade amorphous silicon film (αSi:H) or themicrocrystalline silicon film (μCSi:H) having high microcrystallinefraction of claim 25 is deposited at a substrate temperature of 25°-500°C., and pressure of 0.01 torr to 15 torr.
 28. The solar grade amorphoussilicon film (αSi:H) or the microcrystalline silicon film (μCSi:H)having high microcrystalline fraction of claim 25 is deposited with aprocess selected from the group consisting of Chemical Vapor Deposition(CVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), Low PressureChemical Vapor Deposition (LPCVD), Hot Wire Chemical Vapor Deposition(HWCVD), Initiated Chemical Vapor Deposition (ICVD) and Sub AtmosphericChemical Vapor Deposition (SA-CVD).
 29. The solar grade amorphoussilicon film (αSi:H) or the microcrystalline silicon film (μCSi:H)having high microcrystalline fraction of claim 25 is deposited with aplasma enhanced chemical vapor deposition process at a plasma powerdensity ranging from 0.19-1.6 W/cm² and a plasma frequency ranging from13.56 to 40.68 MHz, at a deposition rate of 10-200 Å/sec for amorphoussilicon film (αSi:H) and 10-100 M/sec for microcrystalline silicon film(μCSi:H).
 30. The solar grade amorphous silicon film (αSi:H) of claim 29provides an Empirical Microstructure Factor R*<20%, and themicrocrystalline silicon film (μCSi:H) having high microcrystallinefraction provides a microcrystalline fraction of >40% and a dark currentactivation energy (Eact) of 0.55-0.65 eV; wherein the EmpiricalMicrostructure Factor R* is defined as R*=I_(HSM)/(I_(LSM)+I_(HSM));wherein I_(HSM) and I_(LSM) correspond to the integrated absorptionstrength of Si—H₂, or the High Stretching Mode (HSM) at 2070-2100 cm⁻¹and the integrated absorption strength of Si—H, or the Low StretchingMode (LSM) at 1980-2010 cm⁻¹.
 31. The solar grade amorphous silicon film(αSi:H) of claim 29 provides a single junction solar cell havingefficiencies of 5-15%, and a tandem junction solar cell havingefficiencies of 7-20%; and the microcrystalline silicon film (μCSi:H)having high microcrystalline fraction of claim 29 provides a tandemjunction solar cell having efficiencies of 7-20%.
 32. A method ofdeposition for a solar grade amorphous silicon film (αSi:H) or amicrocrystalline silicon film (μCSi:H) having high microcrystallinefraction as a photoconductive film on a substrate, using Silane;hydrogen; and at least one additive selected from the group consistingof: (a) halogen substituted higher order silanes, including;1,1-dichlordisilane SiHCl₂SiH₃, 1,1,1,2-tetrafluorodislane SiF₃—SiH₂F,1,2-dichloro-1,2-difluorotetrasilane SiHClF—SiClF—SiH₂—SiH₃,1,1,1-trichlorotrisilane SiCl₃—SiH₂—SiH₃,1,1-difluoro-1,2,2-trichlorosilane SiF₂Cl—SiCl₂—SiH₃, chloropentasilaneSiH₂Cl—(SiH₂)₃—SiH₃, and other compounds of the general formulaSi_(w)H_(2w+2-z)X_(z) where X═F, Cl, Br, I; w can be 1 to 20 and z canbe 1 to 2w+2; 2-chlorotetrasil-2-ene SiH₃—SiCl═SiH—SiH₃,1,1-dichloro-2-fluoropentasil-2-ene SiHCl₂—SiF═SiH₂—SiH₂—SiH₃,2,3-dichlorotetrasil-2-ene SiH₃—SiCl═SiCl—SiH₃, and other compounds ofthe general formula Si_(w)H_(2w-z)X′_(z) where X′═F, Cl, Br, I; and, wcan be 2 to 20 and z can be 1 to 2w; and mixtures thereof; and (b)halogen substituted cyclic higher order silanes, selected from the groupconsisting of; chlorocyclopentasilane Si₅H₉Cl,dodecachlorocyclohexasilane Si₆Cl₁₂, 1-chloro-1fluorocyclopentasilaneSi₅H₈FCl, and mixtures thereof.
 33. The method of deposition for thesolar grade amorphous silicon film (αSi:H) or the microcrystallinesilicon film (μCSi:H) having high microcrystalline fraction of claim 32,wherein the silane used is at 5 to 10%, and the at least one additiveused is at 0.01 to 5%, and the rest is hydrogen.
 34. The method ofdeposition for the solar grade amorphous silicon film (αSi:H) or themicrocrystalline silicon film (μCSi:H) having high microcrystallinefraction of claim 32, wherein the deposition is a process selected fromthe group consisting of Chemical Vapor Deposition (CVD), Plasma EnhancedChemical Vapor Deposition (PECVD), Low Pressure Chemical VaporDeposition (LPCVD), Hot Wire Chemical Vapor Deposition (HWCVD),Initiated Chemical Vapor Deposition (ICVD) and Sub Atmospheric ChemicalVapor Deposition (SA-CVD).
 35. The method of deposition for the solargrade amorphous silicon film (αSi:H) or the microcrystalline siliconfilm (μCSi:H) having high microcrystalline fraction of claim 32, whereinthe deposition is a plasma enhanced chemical vapor deposition at aplasma power density ranging from 0.19-1.6 W/cm² and a plasma frequencyranging from 13.56 to 40.68 MHz.
 36. The method of deposition for thesolar grade amorphous silicon film (αSi:H) or the microcrystallinesilicon film (μCSi:H) having high microcrystalline fraction of claim 35,having a deposition rate of 10-200 Å/sec for amorphous silicon film(αSi:H) and 10-100 Å/sec for microcrystalline silicon film (μCSi:H). 37.The method of deposition for the solar grade amorphous silicon film(αSi:H) or the microcrystalline silicon film (μCSi:H) having highmicrocrystalline fraction of claim 35, wherein the deposited amorphoussilicon film (αSi:H) provides a single junction solar cell havingefficiencies of 5-15%; and the deposited amorphous silicon film (αSi:H)or microcrystalline silicon film (μCSi:H) provides a tandem junctionsolar cell having efficiencies of 7-20%.
 38. A solar grade amorphoussilicon film (αSi:H) or microcrystalline silicon film (μCSi:H) havinghigh microcrystalline fraction deposited using Silane; hydrogen; atleast one additive selected from the group consisting of: (a) halogensubstituted higher order silanes, including; 1,1-dichlordisilaneSiHCl₂SiH₃, 1,1,1,2-tetrafluorodislane SiF₃—SiH₂F,1,2-dichloro-1,2-difluorotetrasilane SiHClF—SiClF—SiH₂—SiH₃,1,1,1-trichlorotrisilane SiCl₃—SiH₂—SiH₃,1,1-difluoro-1,2,2-trichlorosilane SiF₂Cl—SiCl₂—SiH₃, chloropentasilaneSiH₂Cl—(SiH₂)₃—SiH₃, and other compounds of the general formulaSi_(w)H_(2w+2-z)X_(z) where X═F, Cl, Br, I; w can be 1 to 20 and z canbe 1 to 2w+2; 2-chlorotetrasil-2-ene SiH₃—SiCl═SiH—SiH₃,1,1-dichloro-2-fluoropentasil-2-ene SiHCl₂—SiF═SiH₂—SiH₂—SiH₃,2,3-dichlorotetrasil-2-ene SiH₃—SiCl═SiCl—SiH₃, and other compounds ofthe general formula S_(w)H_(2w-z)X′_(z) where X′═F, Cl, Br, I; and, wcan be 2 to 20 and z can be 1 to 2w; and mixtures thereof; and (b)halogen substituted cyclic higher order silanes, selected from the groupconsisting of; chlorocyclopentasilane Si₅H₉Cl,dodecachlorocyclohexasilane Si₆Cl₁₂, 1-chloro-1fluorocyclopentasilaneSi₅H₈FCl, and mixtures thereof.
 39. The solar grade amorphous siliconfilm (αSi:H) of claim 38 provides an Empirical Microstructure FactorR*<20%, and the microcrystalline silicon film (μCSi:H) having highmicrocrystalline fraction of claim 38 provides a microcrystallinefraction of >40% and a dark current activation energy (Eact) of0.55-0.65 eV; wherein the Empirical Microstructure Factor R* is definedas R*=I_(HSM)/(I_(LSM)+I_(HSM)); wherein I_(HSM) and I_(LSM) correspondto the integrated absorption strength of Si—H₂, or the High StretchingMode (HSM) at 2070-2100 cm⁻¹ and the integrated absorption strength ofSi—H, or the Low Stretching Mode (LSM) at 1980-2010 cm⁻¹.
 40. The solargrade amorphous silicon film (αSi:H) or the microcrystalline siliconfilm (μCSi:H) having high microcrystalline fraction of claim 38 isdeposited with the silane at 5 to 10%, the at least one additive used isat 0.01 to 5%, and the rest is hydrogen.
 41. The solar grade amorphoussilicon film (αSi:H) or the microcrystalline silicon film (μCSi:H)having high microcrystalline fraction of claim 38 is deposited at asubstrate temperature of 25°-500° C., and pressure of 0.01 torr to 15torr.
 42. The solar grade amorphous silicon film (αSi:H) or themicrocrystalline silicon film (μCSi:H) having high microcrystallinefraction of claim 38 is deposited with a process selected from the groupconsisting of Chemical Vapor Deposition (CVD), Plasma Enhanced ChemicalVapor Deposition (PECVD), Low Pressure Chemical Vapor Deposition(LPCVD), Hot Wire Chemical Vapor Deposition (HWCVD), Initiated ChemicalVapor Deposition (ICVD) and Sub Atmospheric Chemical Vapor Deposition(SA-CVD).
 43. The solar grade amorphous silicon film (αSi:H) or themicrocrystalline silicon film (μCSi:H) having high microcrystallinefraction of claim 38 is deposited with a plasma enhanced chemical vapordeposition process at a plasma power density ranging from 0.19-1.6 W/cm²and a plasma frequency ranging from 13.56 to 40.68 MHz, at a depositionrate of 10-200 Å/sec for amorphous silicon film (αSi:H) and 10-100 Å/secfor microcrystalline silicon film (μCSi:H).
 44. The solar gradeamorphous silicon film (αSi:H) of claim 43 provides an EmpiricalMicrostructure Factor R*<20%, and the microcrystalline silicon film(μCSi:H) having high microcrystalline fraction provides amicrocrystalline fraction of >40% and a dark current activation energy(Eact) of 0.55-0.65 eV; wherein the Empirical Microstructure Factor R*is defined as R*=I_(HSM)/(I_(LSM)+I_(HSM)); wherein I_(HSM) and I_(LSM)correspond to the integrated absorption strength of Si—H₂, or the HighStretching Mode (HSM) at 2070-2100 cm⁻¹ and the integrated absorptionstrength of Si—H, or the Low Stretching Mode (LSM) at 1980-2010 cm⁻¹.45. The solar grade amorphous silicon film (αSi:H) of claim 43 providesa single junction solar cell having efficiencies of 5-15%, and a tandemjunction solar cell having efficiencies of 7-20%; and themicrocrystalline silicon film (μCSi:H) having high microcrystallinefraction of claim 43 provides a tandem junction solar cell havingefficiencies of 7-20%.